Variolin derivatives as anti-cancer agents

ABSTRACT

The invention provides variolin derivatives of formula (I), wherein: R 1  and R 2  are each independently selected from the group consisting of H, OH, OR, SH, SR, SOR, SO 2 R, NO 2 , NH 2 , NHR, N(R) 2 , NHCOR, N(COR) 2 , NHSO 2 R, CN, halogen, C(═O)H, C(═O)R, CO 2 H, CO 2 R, C 1 -C 12  alkyl, C 1 -C 12  haloalkyl, C 2 -C 12  alkenyl, C 2 -C 12  alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl and substituted or unsubstituted heteroaromatic; and R 3  is selected from the group consisting of H, OH and OMe; wherein the or each group R is independently selected from the group consisting of OH, C 1 -C 12  alkyl, C 1 -C 12  haloalkyl, C 2 -C 12  alkenyl, C 2 -C 12  alkynyl, substituted or unsubstituted aryl, substituted unsubstituted aralkyl, substituted or unsubstituted arylalkenyl and substituted or unsubstituted heteroaromatic, and wherein the group R 1 , R 2  or R 3  is a group of formula N(R) 2  or N(COR) 2 , each of the R groups may be the same or different, or the two R groups, together with the nitrogen atom to which they are attached, may form a 5-14 membered heterocyclic ring. These compounds display activity against a range of mammalian cancer cell lines. New synthetic routes to new and known variolin compounds, together with novel intermediates, are also disclosed. New antitumour activity of known variolin compounds is also described.

FIELD OF THE INVENTION

The present invention relates to antitumoural compounds, and in particular to new antitumoural analogs of variolin B and deoxyvariolin B. The present invention also relates to synthetic processes, and in particular to synthetic processes for producing both the new compounds of the invention and the known compounds variolin B and deoxyvariolin B, including novel intermediates which form a part of such synthetic processes. In addition, the present invention relates to novel, previously undisclosed indications of known variolin compounds.

BACKGROUND OF THE INVENTION

The variolins are a new class of marine alkaloids isolated from the rare, difficult to access Antarctic sponge Kirkpatricka varialosa, with Variolin B (1) being a typical example.

The variolins all contain a fused pyrido [3′,2′:4,5]pyrrolo [1,2-c]pyrimidine core (2), with either a heterocyclic aromatic ring or an ester group attached at C5, as in Variolin B (1) and Variolin D (3).

The variolins are disclosed to have antitumour activity and other useful properties. The complete structure, and antitumour activity, of these and related compounds is described by N. B. Perry et al. Tetrahedron, 1994, 50, 3987-92, and G. Trimurtulu et al, Tetrahedron, 1994, 50, 3993-4000. However, the variolins described in these documents have hitherto only been demonstrated to exhibit a limited range of antitumour activity.

The limited availability of natural material has resulted in the search for alternative synthetic methods being sought for the natural compounds and related analogs.

A synthetic process for producing the related deoxyvariolin B (4) has been described by M. Alvarez et al, Tetrahedron Lett., 2001, 42, 315-317 (which was published before the filing date of the present application but after the priority dates).

The route to deoxyvariolin B described in this reference involves a total of at least fourteen steps, in which the fused tricyclic pyridopyrrolopyrimidine core is constructed from a 7-azaindole and a heteroaryl coupling reaction is then used to introduce the fourth aromatic ring to give intermediate (5). Substitution of the derived sulphone group (6) for an amino group gave deoxyvariolin B (4):

However, as noted above, this synthesis is long and complex. Further, no synthetic process has been reported for variolin B (or any of the natural variolins).

It is therefore desirable to provide a process capable of synthesising deoxyvariolin B and derivatives thereof in a smaller number of steps than the process described above.

It is also desirable to provide a process capable of synthesising variolin B itself as well as the deoxy derivative.

It is further desirable to provide new compounds having antitumour activity comparable or superior to natural variolin B.

The synthetic methods of the present invention provide the first method for preparation of variolin B (1) and provide short, rapid entry to deoxyvariolin B (4) and intermediates such as (5) and (6). These intermediates have been used in the preparation of new antitumour compounds containing the fused tricyclic pyridopyrrolopyrimidine core of the variolins.

SUMMARY OF THE INVENTION

According to this invention, new synthetic methods for producing variolin B, deoxyvariolin B and similar compounds have been developed taking advantage of a hidden symmetry element of these compounds. This novel approach allows construction of the core variolin skeleton, consisting of the fused pyridopyrrolopyrimidine core bearing a heterocyclic aromatic ring at C5, in fewer steps than the prior art synthesis.

Thus, it is possible to transform simple monoheteroaromatic molecules into a number of new and known variolin derivatives with potential antitumour therapeutic activity.

Thus, in a first aspect, the invention provides a compound of formula (I):

wherein:

-   R₁ and R₂ are each independently selected from the group consisting     of H, OH, OR′, SH, SR′, SOR′, SO₂R′, NO₂, NH₂, NHR′, N(R′)₂, NHCOR′,     N(COR′)₂, NHSO₂R′, CN, halogen, C(═O)H, C(═O)R′, CO₂H, CO₂R′, C₁-C₁₂     alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, substituted     or unsubstituted aryl, substituted or unsubstituted aralkyl and     substituted or unsubstituted heteroaromatic; and -   R₃ is selected from the group consisting of H, OH and OMe; -   wherein the or each group R′ is independently selected from the     group consisting of OH, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂     alkenyl, C₂-C₁₂ alkynyl, substituted or unsubstituted aryl,     substituted or unsubstituted aralkyl, substituted or unsubstituted     arylalkenyl and substituted or unsubstituted heteroaromatic, -   and wherein the group R₁, R₂ or R₃ is a group of formula N(R′)₂ or     N(COR′)₂, each of the R′ groups may be the same or different, or the     two R′ groups, together with the nitrogen atom to which they are     attached, may form a 5-14 membered heterocyclic ring; the aryl group     and the aryl moiety of the aralkyl and arylalkenyl group is a     carbocyclic aryl group having from 6 to 14 carbon atoms in a     carbocyclic ring or two or more fused rings; -   the aralkyl group is a C₁-C₆ alkyl group which is substituted by an     aryl group as defined above; -   the arylalkenyl group is a C₂-C₆ alkenyl group which is substituted     by an aryl group as defined above; -   the heteroaromatic group is a heterocyclic aromatic group having     from 5 to 14 ring atoms in one ring or two or more fused rings of     which at least one ring atom is selected from the group consisting     of nitrogen, oxygen and sulphur, and such a heterocyclic aromatic     group fused with an aryl group as defined above; -   the substituents on the aryl and heteroaromatic groups and the aryl     moiety of the aralkyl and arylalkenyl groups are selected from the     group consisting of C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy,     C₁-C₁₂ alkylthio, NH₂, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄     alkanoylamino, di(C₁-C₄ alkanoyl)amino, NO₂, CN and halogen; -   and derivatives thereof where the nitrogen atom is quaternised, -   and salts and esters thereof, -   with the exception of the compounds wherein: -   R₁ is amino, thiomethyl, methylsulfinyl or methylsulfonyl, R₂ is     amino and R₃ is hydrogen; or -   R₁ and R₂ are amino and R₃ is hydroxy.

The invention also provides a synthetic process for producing both the new variolin derivatives of formula (I) described above and known variolin derivatives such as those described in the prior at

Thus, in a second aspect, the invention provides a process for producing a compound of formula (I):

-   -   wherein:

-   R₁ and R₂ are each independently selected from the group consisting     of H, OH, OR′, SH, SR′, SOR′, SO₂R′, NO₂, NH₂, NHR′, N(R′)₂, NHCOR′,     N(COR′)₂, NHSO₂R′, CN, halogen, C(═O)H, C(═O)R′, CO₂H, CO₂R′, C₁-C₁₂     alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, substituted     or unsubstituted aryl, substituted or unsubstituted aralkyl and     substituted or unsubstituted heteroaromatic; and

-   R₃ is selected from the group consisting of H, OH and OMe;

-   wherein the or each group R′ is independently selected from the     group consisting of OH, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂     alkenyl, C₂-C₁₂ alkynyl, substituted or unsubstituted aryl,     substituted or unsubstituted aralkyl, substituted or unsubstituted     arylalkenyl and substituted or unsubstituted heteroaromatic,

-   and wherein the group R₁, R₂ or R₃ is a group of formula N(R′)_(z)     or N(COR′)₂, each of the R′ groups may be the same or different, or     the two R′ groups, together with the nitrogen atom to which they are     attached, may form a 5-14 membered heterocyclic ring;

-   the aryl group and the aryl moiety of the aralkyl and arylalkenyl     group is a carbocyclic aryl group having from 6 to 14 carbon atoms     in a carbocyclic ring or two or more fused rings;

-   the aralkyl group is a C₁-C₆ alkyl group which is substituted by an     aryl group as defined above;

-   the arylalkenyl group is a C₂-C₆ alkenyl group which is substituted     by an aryl group as defined above;

-   the heteroaromatic group is a heterocyclic aromatic group having     from 5 to 14 ring atoms in one ring or two or more fused rings of     which at least one ring atom is selected from the group consisting     of nitrogen, oxygen and sulphur, and such a heterocyclic aromatic     group fused with an aryl group as defined above;

-   the substituents on the aryl and heteroaromatic groups and the aryl     moiety of the aralkyl and arylalkenyl groups are selected from the     group consisting of C₁-C₁₂ alky, C1-C₁₋₂ haloalkyl, C₁-C₁₂ alkoxy,     C₁-C₁₂ alkylthio, NH₂, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄     alkanoylamino, di(C₁-C₄ alkanoyl)amino, NO₂, CN and halogen;

-   and derivatives thereof where the nitrogen atom is quaternised,

-   and salts and esters thereof,

-   the process including the production of an intermediate of formula     (II)     wherein:

-   R_(1a), R_(2a) and R_(3a) represent any of the groups represented by     R₁, R₂ and R₃ respectively, and all such groups where reactive     functional groups are protected; and

-   Y₁ and Y₂ are groups capable of being eliminated to produce a fused     tricyclic pyridopyrrolopyrimidine ring structure.

As described below, the new compounds of formula (I) demonstrate biological activity against mammalian cancer cell lines. Antitumoural activities of these compounds include leukaemias, lung cancer, colon cancer, kidney cancer, prostate cancer, ovarian cancer, breast cancer, sarcomas and melanomas. Further, the known compounds of formula (I) exhibit previously undisclosed activity against a wide range of cancers.

Thus, in a third aspect, the invention provides a method for the treatment or prophylaxis of cancer in a mammal, which comprises administering to a mammal in need of such treatment an effective amount of a new compound of the invention.

Further, in a fourth aspect, the invention provides a method for the treatment or prophylaxis of cancers selected from ovarian cancer, kidney cancer, prostate cancer, breast cancer and melanoma in a mammal, which comprises administering to a mammal in need of such treatment an effective amount of either a new compound of the invention or a variolin compound of the prior art.

In further aspects, the invention provides synthetic steps to certain preferred compounds, described in more detail later, and to intermediate compounds, especially those of formula (II) above.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the definitions used in the present application, alkyl groups may be straight or branched chain groups and preferably have from 1 to about 12 carbon atoms, more preferably 1 to about 8 carbon atoms, still more preferably 1 to about 6 carbon atoms, and most preferably 1, 2, 3 or 4 carbon atoms. Methyl, ethyl and propyl including isopropyl are particularly preferred alkyl groups in the compounds of the present invention. As used herein, the term alkyl, unless otherwise modified, refers to both cyclic and noncyclic groups, although cyclic groups will comprise at least three carbon ring members.

Haloalkyl groups are alkyl groups (including cycloalkyl groups) as defined above which are substituted with one or more halogen atoms (preferably fluorine, chlorine, bromine or iodine) and preferably have from 1 to about 12 carbon atoms, more preferably 1 to about 8 carbon atoms, still more preferably 1 to about 6 carbon atoms, and most preferably 1, 2, 3 or 4 carbon atoms. Methyl, ethyl and propyl including isopropyl groups which are substituted with 1, 2 or 3 halogen atoms which may be the same or different, especially fluoromethyl, fluorochloromethyl, trifluoromethyl and trichloromethyl, are particularly preferred haloalkyl groups in the compounds of the present invention.

Preferred alkenyl and alkynyl groups in the compounds of the present invention have one or more unsaturated linkages and from 2 to about 12 carbon atoms, more preferably 2 to about 8 carbon atoms, still more preferably 2 to about 6 carbon atoms, even more prefereably 2, 3 or 4 carbon atoms. The terms alkenyl and alkynyl as used herein refer to both cyclic and noncyclic groups, although straight or branched noncyclic groups are generally more preferred.

Preferred alkoxy groups in the compounds of the present invention include groups having one or more (but preferably only one) oxygen linkages and from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms, and most preferably 1, 2, 3 or 4 carbon atoms.

Preferred alkylthio groups in the compounds of the present invention have one or more (but preferably only one) thioether linkages and from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms. Alkylthio groups having 1, 2, 3 or 4 carbon atoms are particularly preferred.

Preferred alkylsulfinyl groups in the compounds of the present invention include those groups having one or more sulfoxide (SO) groups and from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms. Alkylsulfinyl groups having 1, 2, 3 or 4 carbon atoms are particularly preferred.

Preferred alkylsulfonyl groups in the compounds of the present invention include those groups having one or more sulfonyl (SO₂) groups and from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms. Alkylsulfonyl groups having 1, 2, 3 or 4 carbon atoms are particularly preferred.

Preferred alkanoyl groups in the compounds of the present invention include those groups having one or more carbonyl (CO) groups and from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms (including the carbonyl carbon). Alkanoyl groups having 1, 2, 3 or 4 carbon atoms, especially the formyl, acetyl, propionyl, butyryl and isobutyryl groups, are particularly preferred.

Preferred alkylamino groups in the compounds of the present invention have one or more (but preferably only one) NH linkages and from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms. Alkylamino groups having 1, 2, 3 or 4 carbon atoms, especially the methylamino, ethylamino, propylamino and butylamino groups, are particularly preferred.

Preferred dialkylamino groups in the compounds of the present invention have one or more (but preferably only one) nitrogen atom bonded to two alkyl groups, each of which may from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms. The alkyl groups may be the same or different Dialkylamino groups wherein each alkyl group has 1, 2, 3 or 4 carbon atoms, especially the dimethylamino, diethylamino, N-methylethylamino, N-ethylpropylamino, dipropylamino, dibutylamino and N-methylbutylamino groups, are particularly preferred.

Preferred alkanoylamino groups in the compounds of the present invention have one NH—CO— linkage bonded to an alkyl group having from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms. Alkanoylamino groups having 1, 2, 3 or 4 carbon atoms, especially the formylamino, acetylamino, propionylamino and butyrylamino groups, are particularly preferred. The acetylamino group is especially preferred.

Preferred dialkanoylamino groups in the compounds of the present invention have one nitrogen atom bonded to two alkanoyl groups as defined above, each of which may be the same or different and has from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms.

Dialkanoylamino groups wherein each alkanoyl group has 1, 2, 3 or 4 carbon atoms, especially the diformylamino, formylacetylamino, diacetylamino, dipropionylamino and dibutyrylamino groups, are particularly preferred. The diacetylamino group is especially preferred.

Preferred alkylsulfonylamino groups in the compounds of the present invention have one NH—SO₂— linkage bonded to an alkyl group having from 1 to about 12 carbon atoms, more preferably from 1 to about 8 carbon atoms, and still more preferably 1 to about 6 carbon atoms. Alkylsulfonylamino groups having 1, 2, 3 or 4 carbon atoms, especially the methanesulfonylamino, ethanesulfonylamino, propanesulfoylamino and butanesulfonylamino groups, are particularly preferred.

In the compounds of formula (I), R₁ is preferably selected from the group consisting of OH, OR′, SH, SR′, SOR′, SO₂R′, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂, NHSO₂R′, C(═O)R′, CO₂H, CO₂R′, C₁-C₁₂ alkyl and C₁-C₁₂ haloalkyl,

-   the or each group R′ being independently selected from the group     consisting of OH, C₁-C₁₂ alky, C₁-C₁₂ haloalkyl, aryl (which may     optionally be substituted with a group selected from C₁-C₆ alkyl,     C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆ alkylamino, di(C₁-C₆     alkyl)amino, NO₂, CN and halogen), aralkyl or arylalkenyl (the aryl     moiety of which may optionally be substituted with a group selected     from C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆     alkylamino, di(C₁-C₆ alkyl)amino, NO₂, CN and halogen), and wherein     the group R₁ is a group of formula N(R′)₂ or N(COR′)₂, each of the     R′ groups may be the same or different, or the two R′ groups,     together with the nitrogen atom to which they are attached, form a     5-12 membered heterocyclic ring.

More preferably, R₁ is selected from the group consisting of OR′, SR′, SOR′, NH₂, NHR′, N(R)₂, NHCOR′, N(COR′)₂ and NHSO₂R′, the or each group R′ being independently selected from the group consisting of C₁-C₆ alkyl, C₁-C₆ haloalkyl, aryl (which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkenyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), and wherein the group R₁ is a group of formula N(R′)₂ or N(COR′)₂, the two R′ groups, together with the nitrogen atom to which they are attached, may form a 5-10 membered heterocyclic ring.

Even more preferably, R₁ is selected from the group consisting of C₁-C₄ alkoxy, C₁-C₄ alkylthio, C₁-C₄ alkylsulfinyl, amino, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄ alkanoylamino, di(C₁-C₄ alkanoyl)amino, C₁-C₄ haloalkanoylamino, arylamino (wherein the aryl moiety may optionally be substituted with a C₁-C₄ alkoxy group), benzylamino (wherein the phenyl part of the benzyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), cinnamoylamino or dicinnamoylamino (wherein the phenyl part of the or each cinammoyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), or a 5- to 7-membered nitrogen-containing heterocyclic ring attached to the remainder of the molecule via its nitrogen atom.

Still more preferably, R₁ is selected from methoxy, thiomethyl, methylsulfinyl, amino, methylamino, ethylamino, benzylamino, acetylamino, trifluoroacetylamino, diacetylamino, cinnamoylamino, dicinnamoylamino, p-methoxybenzylamino and piperidino.

Most preferably R₁ is selected from amino, benzylamino, acetylamino, trifluoroacetylamino, diacetylamino, cinnamoylamino, dicinnamoylamino and p-methoxybenzylamino.

R₂ is preferably selected from the group consisting of OH, OR′, SH, SR′, SOR′, SO₂R′, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂, NHSO₂R′, C(═O)R′, CO₂H, CO₂R′, C1-C₁₋₂ alkyl and C₁-C₁₂ haloalkyl,

-   the or each group R′ being independently selected from the group     consisting of OH, C—C₁₂ alkyl, C₁-C₁₂ haloalkyl, aryl (which may     optionally be substituted with a group selected from C₁-C₆ alkyl,     C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆ alkylamino, di(C₁-C₆     alkyl)amino, NO₂, CN and halogen), aralkyl or arylalkenyl (the aryl     moiety of which may optionally be substituted with a group selected     from C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆     alkylamino, di(C₁-C₆ alkyl)amino, NO₂, CN and halogen), and wherein     the group R₂ is a group of formula N(R′)₂ or N(COR′)₂, each of the     R′ groups may be the same or different, or the two R′ groups,     together with the nitrogen atom to which they are attached, form a     5-12 membered heterocyclic ring.

More preferably, R₂ is selected from the group consisting of OR′, SR′, SOR′, NH₂, NHR, N(R′)₂, NHCOR′, N(COR′)₂ and NHSO₂R′, the or each group R′ being independently selected from the group consisting of C₁-C₆ alkyl, C₁-C₆ haloalkyl, aryl (which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkenyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), and wherein the group R₂ is a group of formula N(R′)₂ or N(COR′)₂, the two R′ groups, together with the nitrogen atom to which they are attached, may form a 5-10 membered heterocyclic ring.

Even more preferably, R₂ is selected from the group consisting of C₁-C₄ alkoxy, C₁-C₄ alkylthio, C₁-C₄ alkylsulfinyl, amino, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄ alkanoylamino, di(C₁-C₄ alkanoyl)amino, C₁-C₄ haloalkanoylamino, arylamino (wherein the aryl moiety may optionally be substituted with a C₁-C₄ alkoxy group), benzylamino (wherein the phenyl part of the benzyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), cinnamoylamino or dicinnamoylamino (wherein the phenyl part of the or each cinammoyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), or a 5- to 7-membered nitrogen-containing heterocyclic ring attached to the remainder of the molecule via its nitrogen atom.

Yet more preferably, R₂ is selected from thiomethyl, methylsulfinyl, amino, methylamino, ethylamino, acetylamino, diacetylamino, cinnamoylamino, and p-methoxybenzylamino.

Most preferably, R₂ is selected from amino, acetylamino, diacetylamino and p-methoxybenzylamino.

Preferably, R₃ is H.

As the person skilled in the art will readily appreciate, the preferred definitions of R₁, R₂ and R₃ above may be combined in various ways, and the compounds covered by such combinations of the above preferred definitions are to be considered as being part of this invention. A combination of two of these definitions is preferred, and a combination of all three preferred definitions is especially preferred.

The following compounds are most preferred:

-   N′-bisacetyldeoxyvariolin; -   N′-bisacetyl-N-acetyldeoxyvariolin; -   N′-bisacetyl-N-bisacetyldeoxyvariolin; -   N′-acetyldeoxyvariolin; -   N′-acetyl-N-acetyldeoxyvariolin; -   N′-biscinnamoyldeoxyvariolin; -   N′-biscinnamoyl-N-cinnamoyldeoxyvariolin; -   N′-methanesulfonyldeoxyvariolin; -   N′-trifluoroacetyldeoxyvariolin; -   2′-methoxydeoxyvatiolin; -   2′-piperidinyldeoxyvariolin; -   N′-ethyldeoxyvariolin; -   N′-butyl-N′-methyldeoxyvariolin; and -   N′-benzyldeoxyvariolin.

The compounds of formula (I) contain a basic group, and may therefore form a salt. The nature of such salts is not critical to the present invention, provided that, when the compound is used for therapeutic purposes, the salts are pharmaceutically acceptable, ie more biologically active, about as biologically active or not unduly less biologically active than the free base compound, and less toxic, about as toxic or not unduly more toxic than the free base compound. This can easily be ascertained by simple tests readily apparent to those skilled in the art. However, when the compound is used for other purposes (for example, as an intermediate in the preparation of another compound) even this restriction does not apply. Examples of suitable salts include inorganic acid salts such as hydrochloride, hydrobromide, sulfate and phosphate; organic acid salts such as acetate, benzoate, oxalate, maleate, fumarate, tartrate, citrate and succinate; and sulfonic acid salts such as methanesulfonate, benzenesulfonate and p-toluenesulfonate. Preferred salts include hydrochloride, hydrobromide, tartrate and succinate.

Some of the compounds of formula (I) contain a carboxy group, and may therefore form an ester. The nature of such esters is not critical to the present invention, provided that, when the compound is used for therapeutic purposes, the esters are pharmaceutically acceptable, ie more biologically active, about as biologically active or not unduly less biologically active than the free acid compound, and less toxic, about as toxic or not unduly more toxic than the free acid compound. It is preferred that the ester group is physiologically removable, ie the ester can be readily converted in vivo to the free acid. This can easily be ascertained by simple tests readily apparent to those skilled in the art.

The compounds of the present invention contain at least four tertiary amine groups, of which one or more (but preferably only one) may be quaternised to form a quaternary ammonium salt. In this case, a counter ion is also present; examples of suitable counter ions are defined above with reference to salts. The procedure for quaternising the nitrogen atom(s) is readily apparent to those skilled in the art. It is preferred that the group attached to the tertiary amino group to form a quaternary ammonium species is a C₁-C₆ alkyl group, most preferably a methyl group.

The variolin derivatives of formula (I), including the known variolin compounds, are produced by a novel process which forms part of the present invention.

An element of the process of the invention involves the formation of the intermediate of formula (II) below:

In the intermediate of formula (II), R_(1a), R_(2a) and R_(3a) represent any of the groups represented by R₁, R₂ and R₃ respectively, and all such groups where reactive functional groups are protected; and Y₁ and Y₂ are groups capable of being eliminated to produce a fused tricyclic pyridopyrrolopyrimidine ring structure. The intermediates of formula (II) are novel compounds and also form part of the present invention.

Any protecting group known in the art may be used to form the groups R_(1a), R_(2a) and R_(3a) with reactive functionalities protected. In this regard, reference is made to T. W. Greene et al, “Protective Groups in Organic Synthesis”, John Wiley & Sons, 1991.

Any groups capable of being eliminated to produce a fused tricyclic pyridopyrrolo-pyrimidine ring structure may be used as the groups Y₁ and Y₂. Preferably the group Y, is a hydroxy group or a labile ester group such as acetate, methanesulfonate, p-toluenesulfonate or trifluoromethanesulfonate, more preferably a hydroxy group. Preferably the group Y₂ is a halogen atom, more preferably a chlorine atom.

It is preferred that the intermediate of formula (II) is symmetrical, ie R_(1a) and R_(2a) are the same: as described below, this allows the intermediate to be made by addition of two equivalents of reagent to a precursor; this in turn shortens the synthesis. More preferably, R_(1a) and R_(2a) are both methylthio groups.

The intermediate of formula (II) can be made by a number of methods. One preferred method is by reacting an intermediate compound of formula (IV):

wherein R_(3a) and Y₂ are as defined above and M is a metal, with a compound of formula (V):

wherein R_(1a) and R_(2a) are as defined above.

In the compound of formula (IV) above, the nature of the metal atom M is not particularly critical, provided that the compound is sufficiently reactive to undergo addition to the compound of formula (V). Examples of suitable metallated species include those where M is Li, Na, K, Mg or Zn; in the case of metallated species with divalent metal ions, a further counterion such as halogen may also be present, or the compound may be in the form of a diorganometallic species. We prefer that M is Li.

The compound of formula (IV) is typically produced in situ by metallating the corresponding halo compound. Suitable reagents are well known in the art, and examples include the metal itself or another more active metallating compound such as an alkylmetal derivative. Alkyllithium derivatives are preferred and butyllithium is especially preferred.

The compound of formula (V) is preferably produced by reacting an intermediate compound of formula (VI):

wherein R_(1a) is as defined above and M is a metal, with a compound of formula L₁-CO-L₂, where L₁ and L₂ are the same or different and each represents a leaving group.

In the compound of formula (VI), the nature of the metal atom M is not particularly critical, provided that the compound is sufficiently reactive to undergo addition to the compound of formula L, —CO-L₂. Examples of suitable metallated species include those defined and exemplified above in relation to the compound of formula (IV). We prefer that M is Li.

The compound of formula (VI) is typically produced in situ by metallating the corresponding halo compound, ie a compound of formula (VIII):

wherein R_(1a) is as defined above and X is a halogen atom, preferably bromine or iodine.

The compound of formula (VIII) where R_(1a) is methylthio and X is chloro is commercially available. Corresponding compounds where X is another halogen atom can be prepared from the corresponding chloro compound as described in the literature, see Majeed, A. J.; Antonsen. O.; Benneche, T.; Undheim, K. Tetrahedron, 1989, 45, 993 and Reference Example 1 below.

Suitable reagents and procedures for metallating the compound of formula (VIII) to produce the compound of formula (VI) are known in the art. Examples include the metal itself or another more active metallating compound such as an alkylmetal derivative. Alkyllithium derivatives are preferred and butyllithium is especially preferred.

In the compound of formula L₁-CO-L₂, L₁ and L₂ may be the same or different and each represents a leaving group, the precise nature of which is not especially critical. Non-limiting examples of suitable leaving groups include halogen, C₁-C₆ alkoxy, di(C₁-C₆ alkyl)amino, nitrogen-containing heterocyclic (especially imidazole) or a labile ester group such as those defined above in relation to Y₁. Diethyl carbonate is a particularly preferred example of a compound of formula LI-CO-L₂.

In an alternative preferred embodiment, the compound of formula (II) is produced by reacting an intermediate compound of formula (VI), described above, with an intermediate compound of formula (VII):

wherein R_(3a) and Y₂ are as defined above, and Z is a leaving group.

In the compound of formula (VI), the group Z is a leaving group, examples of which are defined above with reference to Y₁, L₁ and L₂. It is particularly preferred that Z is a halogen atom, especially chlorine, as two equivalents of the metallated compound of formula (VI) can add cleanly to the compound of formula (VII).

On elimination of the groups Y₁ and Y₂, the intermediate of formula (I) preferably cyclises to produce an intermediate of formula (III):

wherein R_(1a), R_(2a) and R_(3a) are as defined above.

The elimination of the groups Y₁ and Y₂ is preferably carried out by reacting the intermediate of formula (II) with a trialkylsilane of formula R_(a)R_(b)R_(c)SiH wherein R_(a), R_(b) and R_(c) may be the same or different and each represents a C₁-C₁₂ alkyl group. Preferably triethylsilane is used as the reagent.

The reaction is preferably carried out in the presence of acid, the precise nature of which is not particularly critical. A strong organic acid such as p-toluenesulfonic acid or trifluoroacetic acid is preferred and trifluoroacetic acid is especially preferred.

The intermediate compound of formula (III) may then be converted to a compound of formula (I) by functional group interconversions, the general nature of which is known to those skilled in the art By way of example, the amine groups of the known compound deoxyvariolin B (4), prepared by the process of the present invention, may readily be converted into a variety of functionalised derivatives as shown in Scheme I and exemplified below.

In an alternative approach, a further group of analogs may be generated by functionalisation of the C5 heteroaromatic ring of the variolins. This can be readily achieved from intermediate (5) by oxidation to the sulphone (6) or sulphoxide (22) followed by nucleophilic substitution reactions, as shown in Scheme II.

Two particularly important interconversions have not previously been demonstrated for the variolins.

Therefore, in a further aspect, the invention provides a process for producing a compound of formula (I) wherein R₁ and R₂ are amino groups and R₃ is as defined above, said process comprising:

-   a) treating a compound of formula (I), wherein R_(1a) and R_(2a) are     methylsulfinyl and R_(3a) is as defined above, with a compound of     formula NH₂Prot, where Prot is an amino-protecting group, to give a     compound of formula (III), wherein R_(1a) and R_(2a) are protected     amino and R_(3a) is as defined above, and -   b) removing the amino-protecting group to give a compound of     formula (I) wherein R₁ and R₂ are amino groups and R₃ is as defined     above.

The nature of the amino-protecting group is not especially critical. Examples of suitable protecting groups, their attachment and their removal are given in T. W. Greene et al, “Protective Groups in Organic Synthesis”, John Wiley & Sons, 1991, to which reference is made.

It is preferred that the protecting group is a substituted or unsubstituted benzyl group or a phthalimide group, especially a p-methoxybenzyl (PMB) group. The group may be removed by any conventional route, such as under acid conditions (especially a strong organic acid, for example trifluoromethanesulfonic acid or trifluoroacetic acid), under oxidising conditions, for example dichlorodicyanobenzoquinone (DDQ) or reductive conditions, for example with hydrogen and a palladium catalyst.

A preferred embodiment of such a process is illustrated in Scheme III below, in which the conversion of disulphoxide (20) into deoxyvariolin B (4) is achieved in two steps via the bis-amine (29).

In a yet further aspect, the invention provides a process for producing a compound of formula (I) wherein R₁ is a methylthio or amino group, R₂ is an amino group and R₃ is as defined in claim 1, from a compound of formula (III), wherein R_(1a) and R_(2a) are methylthio and R_(3a) is as defined in claim 19, said process comprising:

-   a) optionally, oxidising the compound of formula (R₁) wherein     R_(1a), and R_(2a) are methylthio to a compound of formula (III)     wherein R_(1a) and R_(2a) are methylsulfinyl; and -   b) treating the compound of formula (III) wherein R_(1a) and R_(2a)     are methylthio or methylsulfinyl with a reagent selected from sodium     azide and ammonia

Any oxidising agent capable of oxidising thioethers to sulfoxides may be used to achieve the optional oxidation step a) of the above process. Non-limiting examples of suitable oxidising agents include hydrogen peroxide, sodium periodate, t-BuOCl, sodium perborate, and peracids such as peracetic acid, m-chloroperbenzoic acid (mCPBA) or magnesium monoperoxyphthalate (MMPP), of which peracids are preferred and mCPBA is especially preferred.

An embodiment of such a process is illustrated in Scheme IV below, in which intermediate (19) is converted to deoxyvariolin B (4) in a single step via the sulfoxide intermediate (20):

The novel methodology employed to construct the core variolin skeleton allows the synthesis of deoxyvariolin B (4) to be completed in a total of only five steps from the simple monoheteroaromatic staring material (7). This synthesis is significantly shorter than the sequence to deoxyvariolin B described in the prior art.

In an alternative embodiment of such a process, illustrated in Scheme V below, dithioether intermediate (19) is converted into thiodeoxyvariolin (5) in a single step by treatment with ammonia solution:

A particularly preferred embodiment of the process of the present invention is illustrated in Scheme VI below. The precise conditions are described in more detail in the Examples, Process Examples and Reference Examples.

The novel synthetic approach of the present invention allows construction of the core variolin skeleton, consisting of the fused pyridopyrrolopyrimidine core bearing a heterocyclic aromatic ring at C5, as in (13), in only four steps from the simple monoheteroaromatic starting material (7).

Straightforward functional group manipulation then allows the conversion of intermediate (13) to the known compound variolin B (1) in four further steps, as illustrated in Scheme VII below:

This short eight step sequence from commercially available starting material (7) represents the first reported synthetic process for the preparation of variolin B.

Similar methodology provides rapid access to the key intermediate (19) useful for the synthesis of deoxy variolin B and related analogs, as illustrated in Scheme VIII below and described in more detail in the Examples, Process Examples and Reference Examples.

The routes described above to variolin B or deoxyvariolin B can be conveniently modified to form other derivatives. In particular, this invention provides new compounds that can be made from intermediates prepared by a new process that is part of this invention.

Thus, according to the present invention, we now provide synthetic routes for the production of variolin B (1), deoxyvariolin B (4) and related intermediates such as (5) and thus for the production of variolin analogs. The synthetic routes of the invention each comprise a number of transformation steps to arrive at the desired product. Each step in itself is a process in accordance with this invention. The invention is not limited to the routes that are exemplified, and alternative routes may be provided by, for example, changing the order of the transformation steps, as appropriate.

In more detail, the synthesis of variolin B according to an especially preferred embodiment of the current invention involves the following eight steps.

-   -   (a) conversion of commercially available         4-chloro-2-thiomethylpyrimidine (7) to the iodo compound (8),     -   (b) reaction of (8) with diethyl carbonate to give the symmetric         ketone (9),     -   (c) addition of (9) to a solution of the lithiated form of         pyridine derivative (1) to form the triaryl alcohol (12),     -   (d) tandem deoxygenation and cyclization of the triaryl         alcohol (12) using a combination of triethylsilane and         trifluoroacetic acid,     -   (e) oxidation of intermediate (13) with mCPBA to the         disulphoxide (14),     -   (f) treatment of (14) with p-methoxybenzylamine to give the         bis-amine (15),     -   (g) conversion of the methoxy group of (15) to the alcohol (16)         using sodium ethanethiolate,     -   (h) removal of the p-methoxybenzyl protecting groups of (16)         with triflic acid to give variolin B (1).

This synthesis is illustrated in Scheme IX below. Further details of the processes used are given in the Examples, Process Examples and Reference Examples.

In another preferred modification, starting material (7) is transformed into deoxyvariolin B involving the following five further steps.

-   -   (a) conversion of commercially available         4-chloro-2-thiomethylpyrimidine (7) to the iodo compound (8),     -   (b) reaction of (8) with the pyridine derivative (17) to give         the triaryl alcohol (18),     -   (c) tandem deoxygenation and cyclization of the triaryl         alcohol (18) using a combination of triethylsilane and         trifluoroacetic acid,     -   (d) oxidation with mCPBA of dithioether (19) to the disulphoxide         (20),     -   (e) treatment of (20) with ammonia solution to give         deoxyvariolin B (4).

This synthesis is illustrated in Scheme X below. Further details of the processes used are given in the Examples, Process Examples and Reference Examples.

As the skilled artisan will readily appreciate, the reaction schemes described herein may be modified and/or combined in various ways, and the compounds generated therefore are to be considered as being part of this invention. In particular the starting material and/or reagents and reactions can be varied to suit other combinations of the substituent groups in the formulae (1) to (VIII).

Pharmaceutical Compositions

Examples of pharmaceutical compositions include any solid (tablets, pills, capsules, granules, etc.) or liquid (solutions, suspensions or emulsions) with suitable composition or oral, topical or parenteral administration, and they may contain the pure compound or in combination with any carrier or other pharmacologically active compounds. These compositions may need to be sterile when administered parenterally.

The correct dosage of the compounds will vary according to the particular formulation, the mode of application, and the particular situs, host and tumour being treated. Other factors like age, body weight, sex, diet, time of administration, rate of excretion, condition of the host, drug combinations, reaction sensitivities and severity of the disease shall be taken into account. Administration can be carried out continuously or periodically within the maximum tolerated dose.

Administration of the compounds or compositions of the present invention may be by any suitable method, such as intravenous infusion, oral preparations, intraperitoneal and intravenous administration.

Cytotoxic Activity

The compounds of the present invention were tested according to the protocol described below.

A colorimetric type of assay, using sulforhodamine B (SRB) reaction has been adapted for a quantitative measurement of cell growth and viability: see Skehan, P. A. et al. J. Natl. Cancer Inst., 1990, 82, 1107-1112. This form of the assay employs 96 well cell culture microplates of 9 mm diameter (Faircloth, G. T.; Stewart, D. and Clement, J. J., Journal of Tissue and Culture Methods, 1983, 11, 201-205; Mosmann, T. Journal of Immunological Methods, 1983, 65, 55-63.).

Most of the cell lines are obtained from American Type Culture Collection (ATCC) derived from different human cancer types. Cells are maintained in RPMI 1640 10% FBS, supplemented with 0.1 g/l penicillin and 0.1 g/l streptomycin sulfate and then incubated at 37° C., 5% CO₂ and 98% humidity. For the experiments, cells were harvested from subconfluent cultures using trypsin and resuspended in fresh medium before plating.

Cells are seeded in 96 well microtiter plates, at 5×103 cells per well in aliquots of 195 μl medium, and they are allowed to attach to the plate surface by growing in drug free medium for 18 hours. Afterward, samples are in aliquots of 5 pi in a ranging from 10 to 10-8 μg/ml dissolved in DMSO/EtOH (0.2% in PS buffer). After 48 hours exposure, the antitumour effect are measured by the SRB methodology: cells are fixed by adding 50 μl of cold 50% (w/v) trichloroacetic acid (TCA) and incubating for 60 minutes at 4° C. Plates are washed with deionized water and dried. 100 μl of SRB solution (0.4% w/v in 1% acetic acid) is added to each microtiter well and incubated for 10 minutes at room temperature. Unbound SRB is removed by washing with 1% acetic acid. Plates are air-dried and bound stain is solubilized with Tris buffer. Optical densities are read on an automated spectrophotometric plate reader at a single wavelength of 490 nm.

The values for mean +/− SD of data from triplicate wells are calculated Some parameters for cellular responses can be calculated: TGI=growth inhibition, TGI=total growth inhibition (cytostatic effect) and LC=cell killing (cytotoxic effect).

The results are shown in Tables 1 and 2 below. Although compounds (1), (4), (5) and (6) are not themselves part of the present invention, the results disclosed in the Tables demonstrate antitumour activity not previously disclosed for these compounds.

This application claims priority from GB application nos. 0017055.5, filed 11 Jul. 2000, and 0030689.4, filed 15 Dec. 2000. The contents of both documents are hereby incorporated by reference to the extent that there is disclosure therein which is not explicitly reproduced in the present specification. TABLE 1 Antitumour in vitro data Tumor Type: NSCLColon  Melanoma COMPOUND Cell line: A-549 HT-29 SW-620 MEL-28 Variolin B 1 GI50 (M): 7.E−07 7.E−07 1.E−07 7.E−07 (Natural origin) TGI (M): 1.E−06 1.E−06 3.E−07 1.E−06 LC50 (M): 3.E−06 3.E−06 2.E−06 2.E−06 Deoxyvariolin 4 GI50 (M): 1.E−07 7.E−08 7.E−08 7.E−08 TGI (M): 2.E−07 2.E−07 3.E−07 1.E−07 LC50 (M): 4.E−07 1.E−05 1.E−05 3.E−07 Thiodeoxyvariolin 5 GI50 (M): 1.E−06 6.E−07 3.E−06 6.E−08 TGI (M): 3.E−06 2.E−06 1.E−05 3.E−07 LC50 (M): 1.E−05 1.E−05 3.E−05 6.E−06 Tumor Type:  Ovary  Kidney  Prostate  Breast COMPOUND Cell line: OVCAR-3 A498 DU-145 MCF-7 MB-231 Variolin B 1 GI50 (M): 1.E−07 1.E−07 7.E−07 3.E−07 (Natural origin) TGI (M): 3.E−07 3.E−07 2.E−06 1.E−06 LC50 (M): 2.E−06 1.E−06 2.E−06 3.E−06 Deoxyvariolin 4 GI50 (M): 1.E−07 7.E−08 1.E−07 1.E−07 7.E−08 TGI (M): 3.E−07 2.E−07 3.E−07 3.E−07 3.E−07 LC50 (M): 4.E−07 7.E−07 7.E−06 4.E−06 3.E−05 Thiodeoxyvariolin 5 GI50 (M): 1.E−06 6.E−07 3.E−07 2.E−06 2.E−06 TGI (M): 2.E−06 2.E−06 1.E−06 6.E−06 6.E−07 LC50 (M): 3.E−06 3.E−06 3.E−06 3.E−05 1.E−05 GI50 50% growth inhibition TGI Total growth inhibition (cytostatic effect) LC50 50% net cell killing (cytotoxic effect)

TABLE 2 Antitumour in vitro data (M) Cpd A-549 HT-29 No MW R₁ R₂ R₃ GI50 TGI LC50 GI50 TGI LC50 19 339.4 SMe SMe H 5.9 10⁻⁶ 1.2 10⁻⁵ 2.9 10⁻⁵ 5.9 10⁻⁶ 1.5 10⁻⁵ 2.9 10⁻⁵ 20 371.4 SOMe SOMe H 5.4 10⁻⁵ >1.3 10⁻⁴   >1.3 10⁻⁴   1.1 10⁻⁴ >1.3 10⁻⁴   >1.3 10⁻⁴   22 324.4 SOMe NH₂ H 1.2 10⁻⁶ 6.2 10⁻⁶ 9.2 10⁻⁵ 9.2 10⁻⁷ 1.5 10⁻⁵ >1.5 10⁻⁴    23a 361.4 N(Ac)₂ NH₂ H 2.8 10⁻⁷ 1.4 10⁻⁶ 2.8 10⁻⁶ 1.4 10⁻⁷ 2.8 10⁻⁷ 2.8 10⁻⁶  23b 403.4 N(Ac)₂ NHAc H 7.4 10⁻⁷ 2.0 10⁻⁶ 7.4 10⁻⁶ 1.0 10⁻⁷ 1.7 10⁻⁶ 2.5 10⁻⁶  23c 445.4 N(Ac)₂ N(Ac)₂ H 2.2 10⁻⁶ 1.3 10⁻⁵ 2.2 10⁻⁵ 1.1 10⁻⁶ 2.0 10⁻⁶ 1.8 10⁻⁵  23d 319.3 NHAc NH₂ H 6.3 10⁻⁷ 1.6 10⁻⁶ 3.2 10⁻⁶ 6.3 10⁻⁷ 1.6 10⁻⁶ 3.2 10⁻⁶  23e 361.4 NHAc NHAc H 2.2 10⁻⁶ 5.5 10⁻⁶ 2.8 10⁻⁵ 5.5 10⁻⁶ >2.8 10⁻⁵   >2.8 10⁻⁵    24a 407.4 N(cinnamyl)₂ NH₂ H 1.2 10⁻⁷ 1.2 10⁻⁶ 1.2 10⁻⁵ 4.9 10⁻⁶ 1.2 10⁻⁵ >1.2 10⁻⁴    24b 667.7 N(cinnamyl)₂ NHcinnamyl H 3.0 10⁻⁶ 7.5 10⁻⁶ 7.5 10⁻⁵ 1.5 10⁻⁶ 1.5 10⁻⁵ 7.5 10⁻⁵ 26 373.3 NHCOCF₃ NH₂ H 2.7 10⁻⁷ 1.3 10⁻⁶ 2.7 10⁻⁵ 8.0 10⁻⁷ 1.3 10⁻⁵ 1.1 10⁻⁴ 27 292.3 OMe NH₂ H 6.8 10⁻⁸ 3.4 10⁻⁷ 2.7 10⁻⁶ 1.7 10⁻⁷ 3.4 10⁻⁷ 3.4 10⁻⁵  28d 367.4 NHBn NH₂ H 1.4 10⁻⁶ 2.7 10⁻⁶ 2.7 10⁻⁵ 1.4 10⁻⁶ 2.4 10⁻⁶ 2.2 10⁻⁵  28b 305.3 NHEt NH₂ H >3.3 10⁻⁵   >3.3 10⁻⁵   >3.3 10⁻⁵   >3.3 10⁻⁵   >3.3 10⁻⁵   >3.3 10⁻⁵    28a 345.4 Piperidinyl NH₂ H 8.7 10⁻⁶ 2.3 10⁻⁵ >2.9 10⁻⁵   5.8 10⁻⁶ 2.0 10⁻⁵ >2.9 10⁻⁵    28c 347.42 NMeBu NH₂ H 2.9 10⁻⁶ 8.7 10⁻⁶ 2.3 10⁻⁵ 2.9 10⁻⁶ 8.7 10⁻⁶ 2.3 10⁻⁵ 29 517.6 NHPMB NHPMB H >9.7 10⁻⁵   >9.7 10⁻⁵   >9.7 10⁻⁵   >9.7 10⁻⁵   >9.7 10⁻⁵   >9.7 10⁻⁵    1 293.3 NH₂ NH₂ OH 1.7 10⁻⁷ 6.8 10⁻⁷ 1.7 10⁻⁴ 1.0 10⁻⁶ 1.7 10⁻⁵ >1.7 10⁻⁴    6 340.4 SO₂Me NH₂ H 4.4 10⁻⁶ 1.5 10⁻⁴ >1.5 10⁻⁴   2.9 10⁻⁵ 1.5 10⁻⁴ >1.5 10⁻⁴  

EXAMPLES

Processes for producing the compounds and intermediates of the present invention are described in the Examples below. In the Process Examples are described processes according to the present invention for producing known compounds. The production of intermediate compounds not part of the present invention is described in the Reference Examples.

General Experimental Details

Unless otherwise stated, all reactions were performed under an inert atmosphere in pre-dried glassware. All organic extracts were washed with water and brine, and dried over MgSO₄ prior to concentration in vacuo. Melting points were determined on a Kofler hot-stage apparatus and are uncorrected.

Example 1 Compound 13

A mixture of triaryl alcohol 12 (100 mg, 0.237 mmol) (prepared as described in Example 16 below) and trifluoroacetic acid (37 μL, 0.48 mmol) were dissolved in 1,2-dichloroethane (0.5 mL). The resulting orange solution was transferred to a Young's tube fitted with a rubber septum, containing triethylsilane (0.30 mL, 1.9 mmol). Under a strong flow of argon, the septum was replaced with a Teflon® screw-cap, and the sealed reaction vessel was heated at 100° C. for 43 h. After cooling, the vessel was opened and the contents diluted with CH₂Cl₂ (12 mL). The solution was neutralised with 5% NaHCO₃ solution (8 mL) and the phases separated. The aqueous layer was repeatedly extracted with CH₂Cl₂ and the organic extracts were worked up according to the standard procedure. Purification of the crude material was achieved by flash chromatography on silica gel using gradient elution (48 to 75% EtOAc/hexanes) to afford in order of elution:

(1) the variolin core structure 13 as a yellow solid (41 mg, 47%):

Mp: 192-194° C.; ¹H NMR (500 MHz, CDCl₃): δ 2.65 (s, 3H), 2.70 (s, 3H), 4.03 (s, 3H), 6.92 (d, J=5.4 Hz, 1H), 7.40 (d, J=5.4 Hz, 1H), 7.71 (d, J=6.8 Hz, 1H), 7.98 (d, J=6.8 Hz, 1H), 8.48 (m, 2H); ¹³C NMR (75 MHz, CDCl₃): δ 14.1, 14.9, 55.6, 101.9, 102.5, 108.5, 110.8, 117.7, 135.9, 138.6, 143.5, 144.3, 154.2, 155.6, 159.6, 161.1, 171.2; HRMS: Calcd for C₁₇H₁₅N₅O³²S₂ (M⁺) 369.0718, found 369.0720. and (2) the uncyclised ether 13a as a viscous gum (28 mg, 28%)

¹H NMR (500 MHz, CDCl₃): δ 2.36 (s, 3H), 2.44 (s, 3H), 3.84 (s, 3H) 6.57 (d, J=5.9 Hz, 1H), 6.80 (d, J=5.9 Hz, 1H), 7.17 (d, J=4.9 Hz, 1H), 7.79 (s, 1H), 8.27 (d, J=5.9 Hz, 1H), 8.30 (d, J=5.9 Hz, 1H), 8.49 (d, J=4.9 Hz, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 14.0 (×2), 56.2, 71.8, 103.5, 106.4, 112.9, 120.8, 150.7, 152.5, 157.1, 158.0, 166.0, 167.1, 167.3, 172.1, 172.4; HRMS: Calcd for C₇H₆ ³⁵ClN₅O₂ ³²S₂ (M) 421.0434, found 421.0444.

Example 2 Compounds 14 and 15

Bis-sulfide 13 (37 mg, 0.10 mmol) was dissolved in CHCl₃ (5 mL) under atmospheric conditions and cooled in a 40° C. bath. A pre-cooled (−40° C.) solution of m-chloroperbenzoic acid in CHCl₃ (10 mg/mL) was added dropwise to the solution until TLC analysis indicated the complete consumption of starting material (approx. 2 equiv of m-CPBA was used). The solution was warmed to room temperature and neutralised with saturated NaHCO₃ solution. This was repeatedly extracted with CH₂Cl₂ and after the standard work-up, a yellow solid was obtained, which was predominantly a mixture of diastereomeric bis-sulfoxides. The crude mixture was used without purification, however the bis-sulfoxides 14 had the following spectroscopic characteristics:

¹H NMR (500 MHz, CDCl₃): (most signals for the diastereoisomers coincide, however, as they represent more than one compound they are all quoted as multiplets) δ 3.02 (m, 3H), 3.19 (m, 3H), 4.12 (m, 3H), 7.00-7.01 (m, 1H), 7.98-7.99 (m, 1H), 8.12-8.14 (m, 1H), 8.48-8.49 (m, 1H), 8.64-8.67 (m, 1H), 8.79-8.81 (m, 1H).

The crude oxidised material was heated with an excess of p-methoxybenzylamine (0.15 mL, 1.1 mmol) at 85° C. for 15 h. The crude red paste was purified by flash chromatography on silica gel using gradient elution (2.5-4% MeOH/CH₂Cl₂). The yellow fractions were re-chromatographed using gradient elution (50% EtOAc/CH₂Cl₂ to 100% EtOAc) to give bis-amine 15 as a yellow solid (43 mg, 78% over two steps).

Mp: 74-77° C.; ¹H NMR (500 MHz, CDCl₃): δ 3.81 (s, 6H), 3.99 (s, 3H), 4.66 (d, J-=5.6 Hz, 2H), 4.85 (d, J=5.5 Hz, 2H), 5.51 (m, 1H), 6.82 (d, J=5.6 Hz, 1H), 6.89-6.91 (m, 4H), 7.00 (d, J=5.2 Hz, 1H), 7.29 (m, 1H), 7.34 (d, J=8.5 Hz, 2H), 7.39 (d, J=8.5 Hz, 2H), 7.43 (m, 1H), 8.16 (d, J=5.6 Hz, 1H), 8.26 (d, J=5.2 Hz, 1H), 10.39 (m, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 44.3, 44.9, 55.3 (2×C₁H₃), 55.5, 101.3, 101.6, 101.8, 111.4, 112.2, 114.0 (×2), 128.5, 128.8, 130.5, 131.4, 137.5, 141.5, 141.9, 144.7, 148.7, 154.6 (br), 158.7, 158.9, 159.4, 160.9, 162.6; HRMS: Calcd for C₃₁H₂₉N₇O₃ M) 547.2332, found 547.2334.

Example 3 Compound 16

NaH (60%, 60 mg, 1.5 mmol) was washed three times with petroleum ether, and suspended in dry DMF (1.5 mL). The stirred suspension was cooled in ice, and ethanethiol (0.14 mL, 1.9 mmol) was added dropwise. After the gas evolution had subsided, the clear solution was stirred at room temperature for 10 min. A portion of the NaSEt solution (1.1 mL) was added to a solution of bis-amine 15 (40 mg, 0.073 mmol) in dry DMF (1.5 mL) and the mixture was stirred at 50 IC for 7 h. After cooling, aqueous NH₄Cl solution was added and the mixture was extracted with EtOAc (×3). The organic extracts were washed three times with water to remove DMF and then worked up as usual. The yellow solid produced was purified by flash chromatography on silica gel using 3% MeOH/CH₂Cl₂ as the eluant to afford alcohol 16 as a yellow solid (34 mg, 87%).

¹H NMR (500 MHz, CDCl₃): δ 3.80 (s, 3H), 3.81 (s, 3H), 4.61 (d, J=5.5 Hz, 2H), 4.85 (d, J=5.4 Hz, 2H), 5.35 (m, 1H), 6.76 (d, J=5.5 Hz, 1H), 6.88-6.92 (m, 4H), 7.03 (d, J=6.8 Hz, 1H), 7.06 (d, J=5.7 Hz, 1H), 7.32 (d, J=8.4 Hz, 2H), 7.40 (d, J=8.4 Hz, 2H), 7.68 (d, J=6.8 Hz, 1H), 8.05 (d, J=5.5 Hz, 1H, 8.29 (d, J=5.7 Hz, 1H), 10.94 (m, 1H), 15.75 (br s, 1H); ¹³C NMR (75 MHz, CDCl₃): a 44.3, 452, 55.3 (2×CH₃), 100.3, 100.5, 106.9, 107.5, 111.4, 114.1 (2×C), 128.8, 129.2, 130.2 (2×C), 137.5, 142.8, 143.8, 145.4, 149.7, 158.6, 158.9, 159.0, 159.5, 159.8, 160.0; HRMS: Calcd for C₃₀H₂₇N₇03 (M⁺) 533.2175, found 533.2185.

Example 4 Compound 19

A mixture of alcohol 18 (prepared as described in Example 17 below) (1.04 g, 2.65 mmol), triethylsilane (3.4 ml, 21.5 mmol) and trifluoroacetic acid (0.81 ml, 10.6 mmol) was refluxed for 3 h. After cooling, the red residue was dissolved in CH₂Cl₂ (40 ml) and a saturated solution of NaHCO₃ was added. The brown mixture was stirred for 1 h at room temperature and the layers were separated. The aqueous layer was extracted with CH₂Cl₂ (3×50 ml) and the combined organic layers were dried, filtered and concentrated under reduced pressure. The red residue was purified by flash chromatography using ethyl acetate:hexane 1:4 to ethyl acetate:hexane 1:3 as eluent to afford the pyridopyrrolopyrimidine 19 (0.3 g, 33%) as a pale yellow solid. ¹H NMR (300 MHz, CDCl₃): 8.64 (dd, J=8.1 and 1.7 Hz, 1H), 8.60 (dd, J=4.6 and 1.7 Hz, 1H), 8.51 (d, J=5.4 Hz, 1H), 8.06 (d, J=6.4 Hz, 1H), 7.82 (d, J=6.6 Hz, 1H), 7.51 (dd, J=8.5 and 4.6 Hz, 1H), 7.34 (d, J=5.4 Hz, 1H), 2.73 (s, 3H), 2.68 (s, 3H).

Example 5 Compounds 20 and 29

Oxidation of bis-sulfide 19 to bis-sulfoxide 20 was carried out by the same procedure described above in Example 2.

A mixture of p-methoxybenzylamine (2 ml) and bis-sulfinyldeoxyvariolin 20 (30 mg, 8.1×10⁵ mol) was stirred at 95° C. for 2 h and evaporated at reduced pressure. The red residue was purified by flash chromatography using DCM/MeOH (0.2%) to DCM/MeOH (2%) as eluent to afford N′,N-bis(p-methoxybenzyl)deoxyvariolin 29 (21 mg, 49%) as a yellow oil. ¹H NMR (300 MHz, CDCl₃): 10.4 (brs, 1H), 8.56 (d, J=7.8 Hz, 1H), 8.31 (d, J=5.4, 1H), 8.27 (dd, J=5.2 and 1.1 Hz, 1H), 7.63 (d, J=6.8 Hz, 1H), 7.42-7.33 (m, 12H), 6.98 (d, J=5.4 Hz, 1H), 6.93-6.89 (m, 4H), 5.52 (brs, 1H), 4.89 (d, J=5.4 Hz, 2H), 4.69 (d, J=5.9 Hz, 2H), 3.81 (s, 3H), 3.80 (s, 3H).

Example 6 Compound 28a

Piperidine (0.04 ml, 0.4 mmol) was added to a solution of sulfinyldeoxyvariolin 22 (7 mg, 2.1×10⁻⁵ mol) (prepared ae described in Process Example 5 below) in THF (2 ml).

The yellow solution was stirred at 70° C. overnight and evaporated at reduced pressure.

The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (3%) as eluent to afford piperidinyldeoxyvariolin 28a (5.6 mg, 78%) as a yellow oil. ¹H NMR (300 MHz, CDCl₃): 8.63 (dd, J=8.4 and 1.5 Hz, 1H), 8.38 (dd, J=4.8 and 1.7 Hz, 1H), 8.35 (d, J=5.4, 1H), 7.60 (d, J=6.6 Hz, 1H), 7.50 (d, J=6.6 Hz, 1H), 7.46 (dd, J=8.0 and 4.6 Hz, 1H), 6.84 (d, J=5.4 Hz, 1H), 3.92 (brs, 4H), 1.73 (brs, 6H). MS (electrospray ionisation, ESI) 346 (M+1).

Example 7 Compound 28b

Ethylamine (0.34 ml, 2M in MeOH) was added to a solution of sulfinyldeoxyvariolin 22 (prepared as described in Process Example 5 below) (11 mg, 3.4×10⁻⁵ mol) in THF (2 ml). The yellow solution was stirred at 70° C. overnight and evaporated at reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (4%) as eluent to afford N′-ethyldeoxyvariolin 28b (5.5 mg, 53%) as a yellow oil. ¹H NMR (300 MHz, CDCl₃): 8.67 (dd, J=7.9 and 1.4 Hz, 1H), 8.36 (d, J=4.4, 1H), 8.22 (d, J=4.8, 1H), 7.52 (brs, 2H), 7.45 (dd, J=7.8 and 4.1 Hz, 1H), 6.93 (d, J=5.1 Hz, 1H), 3.54 (d, J=6.8 Hz, 2H), 1.29 (t, J=7.0, 3H). (ESI) 306 (M+1).

Example 8 Compound 28c

Butylmethylamine (0.029 ml, 0.24 mmol) was added to a solution of sulfinyldeoxyvarolin 22 (prepared as described in Process Example 5 below) (8 mg, 2.4×10⁻⁵ mol) in THF (2 ml). The yellow solution was stirred at 70° C. overnight and evaporated at reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (4%) as eluent to afford N′-butylmethyldeoxyvariolin 28c (2 mg, 62% based on recovered starting material) as a yellow oil. ¹H NMR (300 MHz, CDCl₃): 8.75 (d, 1H), 8.41 (dd, 1H), 8.39 (d, J=5.5, 1H), 7.78 (d, J=6.5 Hz, 1H), 7.68 (d, J=6.5 Hz, 1H), 7.42 (dd, J=8.0 and 4.5 Hz, 1H), 6.89 (d, J=5.6 Hz, 1H), 3.60 (brs, 2H), 3.41 (s, 3H), 1.62 (brs, 4H), 1.05 (brs, 3H). (EST) 348 (M+1).

Example 9 Compound 28d

Benzylamine (0.050 ml, 0.45 mmol) was added to a solution of sulfinyldeoxyvariolin 22 (4 mg, 1.2×10⁵ mol) in THF (1.5 ml). The yellow solution was stirred at 70° C. overnight and evaporated at reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (4%) as eluent to afford N′-benzyldeoxyvariolin 28d (2.1 mg, 47%) as a yellow oil. ¹H NMR (300 MHz, CDCl₃): 8.81 (brs, 1H), 8.75 (d, J=7.1, 1H), 8.64 (d, J=6.0 Hz, 1H), 7.49-7.31 (m, 8H), 6.99 (d, J=6.2 Hz, 1H), 4.78 (d, J=5.8 Hz, 2H). (ESI) 368 (M+1).

Example 10 Compound 27

A solution of sulfonyldeoxyvariolin 6 (prepared as described in Process Example 5 below) (5.8 mg, 1.7×10⁻⁵ mol) in MeOH (2 ml) was added to a solution of sodium methoxide in MeOH (2 ml) at 0° C. The yellow solution was stirred at 24° C. for 4 h, quenched with a saturated solution of NH₄Cl and extracted with ethyl acetate (3×10 ml). The combined organic layers were dried, filtered and evaporated under reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (1%) to DCM/MeOH (3%) as eluent to afford methoxydeoxyvariolin 27 (2.6 mg, 53%) as a yellow solid ¹H NMR (300 MHz, CDCl₃): 8.78 (dd, J=8.1 and 1.5 Hz, 1H), 8.51 (d, J=5.43 Hz, 1H), 8.41 (dd, J=4.6 and 1.5 Hz, 1H), 7.69 (d, J=6.6 Hz, 1H), 7.63 (d, J=6.6 Hz, 1H), 7.50 (dd, J=8.1 and 4.6 Hz, 1H), 7.34 (d, J=5.4 Hz, 1H), 4.14 (s, 3H). (ESI) 293 (M+1).

Example 11 Compound 26

Trifluoroacetic anhydride (6 nil, 4.3×10⁵ mol) was added to a solution of deoxyvariolin 4 (4 mg, 1.4×10¹⁵ mol) in THF (1.5 ml). The yellow solution was stirred at 24° C. overnight and evaporated at reduced pressure. The yellow residue was dissolved in DCM (5 ml) and washed with a saturated solution of NaHCO₃ (4 ml). The organic layer was dried, filtered and evaporated under reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (4%) as eluant to afford N′-trifluoroacetyldeoxyvariolin 26 (0.9 mg, 43% based on recovered starting material) as a yellow oil. ¹H NMR (300 MHz, CDCl₃): 8.99 (dd, J=8.4 and 1.1 Hz, 1H), 8.57 (d, J=5.6 Hz, 1H), 8.42 (dd, J=4.6 and 1.3 Hz, 1H), 7.91 (d, J=6.7 Hz, 1H), 7.79 (d, J=6.6 Hz, 1H), 7.58 (dd, J=8.3 and 4.3 Hz, 1H), 7.52 (d, J=5.6 Hz, 1H). (ESI) 374 (M+1).

Example 12 Compound 25

Methanesulfonyl chloride (5.5 μl, 5×10⁻⁵ mol) was added to a solution of deoxyvariolin 4 (prepared as described in Process Example 2 or 4 below) (5 mg, 1.8×10⁻⁵ mol) and Et₃N (5 μl, 3.6×10 ⁻⁵ mol) in THF (1.5 ml). The yellow solution was stirred at 240 C overnight and evaporated at reduced pressure. The yellow residue was dissolved in DCM (5 ml) and washed with a saturated solution of NaHCO₃ (4 ml). The organic layer was dried, filtered and evaporated under reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (4%) as eluant to afford N′-methanesulfonyldeoxyvariolin 25 (1.5 mg, 46% based on recovered starting material) as a yellow oil. ¹H NMR (300 MHz, CDCl₃): 8.89 (dd, J=7.9 and 1.1 Hz, 1H), 8.76 (d, J=5.7 Hz, 1H), 8.42 (dd, J=42 and 1.2 Hz, 1H), 7.78 (d, J=6.4 Hz, 1H), 7.72 (d, J=6.5 Hz, 1H), 7.64 (d, J=5.6 Hz, 1H), 7.57 (dd, J 8.3 and 4.3 Hz, 1H), 3.15 (s, 3H).

Example 13 Compounds 24a and 24b

Cinnamoyl chloride (9 μl, 5.4×10⁻⁵ mol) was added to a solution of deoxyvariolin 4 (5 mg, 1.8×10⁵ mol) (prepared as described in Process Example 2 or 4 below) and Et₃N (12 μl, 5.4×10⁻⁵ mol) in THF (2 ml). Immediately, DMAP (1 mg, 0.9×10⁻⁵ mol) was added in one portion, the yellow solution was stirred at 24° C. overnight and evaporated at reduced pressure. The yellow residue was dissolved in DCM (5 ml) and washed with a saturated solution of NaHCO₃ (4 ml). The organic layer was dried, filtered and evaporated under reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (1%) to DCM/MeOH (4%) as eluent to afford N′-biscinnamoyldeoxyvariolin 24a (1.1 mg, 21% based on recovered starting material) and N′-biscinnamoyl-N-cinnamoyldeoxyvariolin 24b (0.6 mg, 9% based on recovered starting material) as yellow oils.

¹H NMR (300 MHz, CDCl₃): 8.78 (d, J=6.4, 1H), 8.69 (dd, J=7.4 and 1.1 Hz, 1H), 8.38 (dd, J=4.6 and 1.2 Hz, 1H), 7.91 (d, J=15.3 Hz, 2H), 7.64-7.32 (m, 14H), 6.90 (d, J=15.6 Hz, 2H). (ESI) 560 (M+Na), 538 (M+1).

¹H NMR (300 MHz, CDCl₃): ¹H NMR (300 MHz, CDCl₃): 8.82 (d, J=6.4, 1H), 8.79 (dd, J=7.4 and 1.1 Hz, 1H), 8.58 (dd, J=4.6 and 1.3 Hz, 1H), 8.01-7.82 (m, 4H), 7.71 (d, J=15.3 Hz, 2H), 7.64 (dd, J=8.3 and 4.2 Hz, 1H), 7.58-7.31 (m, 16H), 6.90 (d, J=15.6 Hz, 3H). (ESI) 668 (4+1), 690 (M+Na).

Example 14 Compounds 23a, 23b and 23c

Acetyl chloride (3.5 μl, 4.8×10⁻⁵ mol) was added to a solution of deoxyvariolin 4 (9 mg, 3.2×10⁻⁵ mol) (prepared as described in Process Example 2 or 4 below) and Et₃N (9 μl, 6.5×10⁻⁵ mol) in THF (2 ml). The orange slurry was stirred at 24° C. overnight and evaporated at reduced pressure. The yellow residue was dissolved in DCM (5 ml) and washed with a saturated solution of NaHCO₃(4 ml). The organic layer was dried, filtered and evaporated under reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (5%) as eluent to afford N′-bisacetyldeoxyvariolin 23a (1 mg, 26% based on recovered starting material), N′-bisacetyl-N-acetyldeoxyvariolin 23b (1 mg, 23% based on recovered starting material) and N′-bisacetyl-N-bisacetyldeoxyvariolin 23c (0.5 mg, 10% based on recovered starting material) as yellow oils.

¹H NMR (300 MHz, CDCl₃): 8.76 (d, J=5.6, 1H), 8.68 (dd, J=6.9 and 1.1 Hz, 1H), 8.42 (dd, J=4.1 and 1.2 Hz, 1H), 7.73 (d, J=6.6 Hz, 1H), 7.66 (d, J=6.6 Hz, 1H), 7.54-7.42 (m, 2H), 2.41 (s, 6H). (ESI) 384 (M+Na).

¹H NMR (300 MHz, CDCl₃): 8.82 (d, J=5.6 Hz, 1H), 8.72 (dd, J 7.8 and 1.2 Hz, 1H), 8.53 (dd, J=4.4 and 1.2 Hz, 1H), 7.90 (d, J=6.4 Hz, 1H), 7.87 (d, J=6.5 Hz, 1H), 7.70 (d, J=5.4 Hz, 1H), 7.60 (dd, J=8.3 and 4.9 Hz, 1H), 2.68 (s, 3H), 2.40 (s, 6H). (ESI) 426 (M+Na), 404 (M+1).

¹H NMR (300 MHz, CDCl₃): 8.88 (d, J=5.4 Hz, 1H), 8.63 (dd, J=8.3 and 1.7 Hz, 1H), 8.56 (dd, J=4.6 and 1.3 Hz, 1H), 8.36 (d, J=6.7 Hz, 1H), 7.99 (d, J=6.6 Hz, 1H), 7.75 (d, J=5.5 Hz, 1H), 7.58 (dd, J=8.3 and 4.6 Hz, 1H), 2.43 (s, 12H). (ESI) 468 (M+Na).

Example 15 Compounds 23d and 23e

Acetyl chloride (1.5 μl, 1.8×10⁻⁵ mol) was added to a solution of deoxyvariolin 4 (prepared as described in Process Example 2 or 4 below) (5 mg, 1.8×10⁻⁵ mol) and Et₃N (4 μl, 2.7×10⁻⁵ mol) in THF (1.5 ml) at −78° C. The orange slurry was stirred overnight increasing the temperature very slowly until room temperature and afterwards evaporated at reduced pressure. The yellow residue was dissolved in DCM (5 ml) and washed with a saturated solution of NaHCO₃ (4 ml). The organic layer was dried, filtered and evaporated under reduced pressure. The yellow residue was purified by flash chromatography using DCM/MeOH (1%) to DCM/MeOH (4%) as eluent to afford N′-acetyl-N-acetyldeoxyvariolin 23d (1 mg, 26%) and N′-acetyldeoxyvariolin 23e (0.5 mg, 10%) as yellow oils.

¹H NMR (300 MHz, CDCl₃): 8.83 (dd, J=7.4 and 1.4 Hz, 1H), 8.52 (d, J=6.2, 1H), 8.41 (dd, J=4.2 and 1.4 Hz, 1H), 7.75-7.71 (m, 2H), 7.56-7.48 (m, 1H), 7.39 (d, J=6.3 Hz, 1H), 2.43 (s, 3H). (ESI) 342 (M+Na).

¹H NMR (300 MHz, CDCl₃): 8.91 (dd, J=7.4 and 1.4 Hz, 1H), 8.58 (d, J=6.2, 1H), 8.52 (dd, J=4.2 and 1.4 Hz, 1H), 8.19 (d, J=6.4 Hz, 1H), 8.03 (brs, 1H), 7.85 (d, J=6.5 Hz, 1H), 7.61 (dd, J=8.3 and 4.9 Hz, 1H), 7.39 (d, J=6.1 Hz, 1H), 2.65 (s, 3H), 2.43 (s, 3H). (EST) 384 (M+Na).

Example 16 Compound 12

2-Chloro-4-methoxypyridine (11) (Reference Example 3) (0.633 g, 4.41 mmol) was dissolved in freshly distilled THF (18 mL) and the reaction cooled to below −90° C. n-BuLi in hexanes (1.6 M, 2.9 mL, 4.5 mmol) was added over a period of 17 min to the stirred solution, keeping the temperature below −97° C. The orange solution was then stirred at −78° C. for 1 h, by which time it had become a wine-red colour. The reaction mixture was re-cooled to below −90° C. and a solution of ketone (9) (1.14 g, 4.09 mmol) in THF (10 mL) was added over 11 min, keeping the temperature below −90° C. The dark mixture was stirred at −78° C. for 3.5 h, then quenched with methanol and allowed to warm to room temperature. The reaction mixture was shaken with aqueous NH₄Cl solution, extracted with ethyl acetate (×3) and subjected to standard workup. The crude mixture was purified by flash chromatography on silica gel using gradient elution (70 to 75% EtOAc/hexanes) to give the triaryl alcohol 12 as a cream solid (1.32 g, 76%).

¹H NMR (500 MHz, CDCl₃): δ 2.49 (s, 6H), 3.43 (s, 3H), 6.55 (s, 1H), 6.76 (d, J=5.4 Hz, 1H), 7.39 (d, J=5.4 Hz, 2H), 8.25 (d, J=5.4 Hz, 1H), 8.46 (d, J=5.4 Hz, 2H); ¹³C NMR (75 ME CDCl₃): δ 14.1, 55.8, 78.0, 107.1, 113.7, 124.8, 149.8, 152.3, 157.2, 165.9, 171.0, 171.1; IR (CDCl₃ solution): 3344 cm⁻¹; HRMS: Calcd for C₁₇H₁₆ ³⁵ClN₅O₂ ³²S₂ (M⁺) 421.0434, found 421.0448.

Example 17 Compound 18

BuLi (6.9 ml, 2.5 M in hexane) was added dropwise to a solution of iodopyrimidine 8 (Reference Example 1) (4.3 g, 17 mmol) in THF (50 ml) at −100° C. The black solution was stirred for 30 min at the same temperature. A solution of 2-chloronicotinoyl chloride 17 (1 g, 5.7 mmol) in THF (7 ml), previously cooled at −78° C., was added via cannula. The intense red mixture was stirred for 3 h at −95° C. and a saturated solution of NH₄Cl (50 ml) was added. The layers were separated and the aqueous layer was extracted with diethyl ether (3×100 ml). The combined organic layers were dried, filtered and concentrated under reduced pressure. The red residue was purified by flash chromatography using ethyl acetate:hexane 1:3.5 to ethyl acetate:hexane 1:1.5 as eluent to afford the alcohol 18 (1.3 g, 58%) as a pale orange solid. ¹H NMR (300 MHz, CDCl₃): 8.56 (d, J=5.1H. 2H), 8.37 (dd, J 4.7 and 1.5, 1H), 7.39 (d, J=5.1 Hz, 2H), 7.22 (dd, J=7.8 and 1.9, 1H), 7.17 (dd, J=7.8 and 4.4 Hz, 1H), 2.48 (s, 6H).

Process Example 1 Compound 1 (Variolin)

(This compound is not part of the present invention)

Alcohol 16 (prepared as described in Example 3 above) (33 mg, 0.062 mmol) was dissolved in neat triflic acid (0.4 mL) under atmospheric conditions. The flask was sealed and the deep red solution was left at room temperature for 5 h. The flask was cooled in ice and MeOH (2 mL) was added dropwise. Addition of concentrated aqueous ammonia (2 mL) produced a bright yellow precipitate. The suspension was applied to the top of a chromatography column containing reverse-phase silica, which had been equilibrated with 50% MeOH/water. The yellow suspension was applied to the column with 20% MeOH/water (50 mL). The polarity of the eluting solvent system was decreased to 80% MeOH/water (50 mL), and then to 85% MeOH/water containing 0.1% TFA, whereupon the yellow product began to elute. The bright yellow fractions were combined and concentrated in vacuo to give variolin B as its trifluoroacetate salt MeOH (10 mL) was added, followed by concentrated aqueous ammonia (1-2 mL) to give the free base. Removal of the solvents under reduced pressure, followed by drying (35° C., 0.03 mm Hg) overnight gave variolin B (1) (10 mg, 55%), which was identical in all aspects with the natural material.

Process Example 2 Compound 4 (Deoxyvariolin)

(This compound is not part of the present invention)

A solution of mCPBA (Aldrich 70%) (98 mg, 0.39 mmol) in DCM (4 ml), previously dried over Na₂SO₄, was added dropwise to a cooled (−30° C.) solution of dithioether 19 (Example 4) (61 mg, 0.18 mmol) in DCM (5 ml). The yellow solution was stirred for 15 min at 0° C. A saturated aqueous Na₂S₂O₃ solution (5 ml) was added and the organic layer was washed with a saturated solution of NaHCO₃ (5 ml). The combined aqueous layers were extracted with DCM (3×10 ml). The combined organic extracts were dried, filtered and concentrated. The yellow residue was poured in a sealed tube with dioxane (4 ml) and ammonia solution 32% (8 ml) was added. The brown mixture was stirred for 14 h at 85° C. The resulting yellow mixture was evaporated in vacuo and DCM/MeOH (10:1) (11 ml) were added, the solution dried and the solvent evaporated at reduced pressure. The yellow solid was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (5%) as eluent to afford deoxyvariolin 4 (14 mg, 29%, 2 steps) as a yellow solid. ¹H NMR (300 MHz, DMSO): 8.92 (dd, J=8.1 and 1.5 Hz, 1H), 8.45 (dd, J=4.6 and 1.4 Hz, 1H), 8.22 (d, J=5.5, 1H), 7.68 (d, J=6.6 Hz, 1H), 7.63 (d, J=6.6 Hz, 1H), 7.58 (dd, J=8.1 and 4.6 Hz, 1H), 7.06 (d, J=5.4 Hz, 1H). (ESI) 278 (M+1).

Process Example 3 Compound 5 (Thiodeoxyvariolin)

(This compound is not part of the present invention)

Ammonia solution 32% (3 ml) was added to a solution of dithioether 19 (Example 4) (12 mg, 0.035 mmol) in dioxane (2 ml). The brown mixture was stirred for 14 h at 85° C. in a sealed tube. The resulting yellow mixture was evaporated in vacuo, DCM (5 ml) was added, the solution dried and the solvent evaporated at reduced pressure. The yellow solid was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (3%) as eluent to afford thiodeoxyvariolin 5 (8 mg, 73%) as a yellow solid. ¹H NMR (300 MHz CDCl₃): 8.72 (dd, J=8.1 and 1.5 Hz, 1H), 8.48 (d, J=5.4 Hz, 1H), 8.39 (dd, J=4.8 and 1.6 Hz, 1H), 7.66 (d, J=6.8 Hz, 1H), 7.56 (d, J=6.7 Hz, 1H), 7.48 (dd, J=8.1 and 4.6 Hz, 1H), 7.32 (d, J=5.3 Hz, 1H), 2.67 (s, 3H). (ESI) 309 (M+1).

Process Example 4 Compound 4 (Deoxyvariolin)

(This compound is not part of the present invention)

N′,N-bis (p-methoxybenzyl)deoxyvariolin 29 (Example 5) (15 mg, 2.9×10⁻⁵ mol) was treated with neat triflic acid (1.5 ml) and stirred for 17 h at 24° C. The black solution was evaporated at reduced pressure and the black slurry was dissolved in DCM (4 ml) and washed with a saturated solution of NaHCO₃ (5 ml). The aqueous layer was extracted with DCM (3×5 ml) and the combined organic layers were dried, filtered and evaporated. The brown residue was purified by flash chromatography using DCM/MeOH (1%) to DCM/MeOH (5%) as eluent to afford deoxyvariolin 4 (1.5 mg, 19%) as a yellow solid. ¹H NMR (300 MHz, DMSO): 8.92 (dd, J 8.1 and 1.5 Hz, 1H), 8.45 (dd, J=4.6 and 1.4 Hz, 1H), 8.22 (d, J=5.5, 1H), 7.68 (d, J=6.6 Hz, 1H), 7.63 (d, J=6.6 Hz, 1H), 7.58 (dd, J=8.1 and 4.6 Hz, 1H), 7.06 (d, J=5.4 Hz, 1H). (ESI) 278 (M+1).

Process Example 5 Compounds 6 and 22

(These compounds are not part of the present invention)

A solution of mCPBA (Aldrich 70%) (70 mg, 0.30 mmol) in DCM (3 ml), previously dried over Na₂SO₄, was added dropwise to a solution of thiodeoxyvariolin 5 (39 mg, 0.13 mmol) in DCM (7 ml). The yellow solution was stirred for 2 h at 24° C. A saturated aqueous Na₂S₂O₃ solution (5 ml) was added and the organic layer was washed with a saturated solution of NaHCO₃ (5 ml). The combined aqueous layers were extracted with DCM (3×20 ml). The combined organic extracts were dried, filtered and concentrated. The yellow residue was purified by flash chromatography using DCM/MeOH (2%) to DCM/MeOH (5%) as eluent to afford sulfinyldeoxyvariolin 22 (15 mg, 35%) as a yellow oil and sulfonyldeoxyvariolin 6 (25 mg, 58%) as a yellow solid.

¹H NMR (300 MHz, CDCl₃): 8.86 (dd, J=8.1 and 1.5 Hz, 1H), 8.74 (d, J=5.6 Hz, 1H), 8.43 (dd, J=4.6 and 1.3 Hz, 1H), 7.77 (d, J=6.8 Hz, 1H), 7.72 (d, J=6.6 Hz, 1H), 7.67 (d, J=5.8 Hz, 1H), 7.54 (dd, J=8.0 and 4.6 Hz, 1H), 3.02 (s, 3H). (ESI) 325 (M+1).

¹H NMR (300 MHz, CDCl₃): 8.80 (dd, J=8.1 and 1.4 Hz, 1H), 8.71 (d, J=5.6 Hz, 1H), 8.41 (dd, J=4.8 and 1.4 Hz, 1H), 7.76 (d, J=5.6 Hz, 1H), 7.74 (d, J=6.4 Hz, 1H), 7.64 (d, J=6.4 Hz, 1H), 7.52 (dd, J=8.2 and 4.8 Hz, 1H), 3.40 (s, 3H).

Reference Example 1 Compound 8

Iodopyrimidine 8 was prepared following the experimental procedure described in the literature: Majeed, A. J.; Antonsen. O.; Benneche, T.; Undheim, K. Tetrahedron 1989, 45, 993.

Reference Example 2 Compound 9

A pre-cooled (−97 IC) solution of n-BuLi in hexanes (1.55 M, 10.0 mL, 15.5 mmol) was added slowly over a period of 21 min to a solution of 4-iodo-2-methylthiopyrimidine (8) (3.90 g, 15.5 mmol) in freshly distilled THF (47 mL) at −97° C. (methanol/liquid N₂ bath). Care was taken to prevent the temperature from rising above −97° C. After addition was complete, the dark mixture was stirred for 30 min at −97° C. and then, a pre-cooled (−97° C.) solution of diethyl carbonate (0.94 mL, 7.8 mmol) in THF (4 mL) was added over a period of approx. 3 min. After 15 min at −97° C. the bath was allowed to warm to −35° C. over 2 h, and then to room temperature. The reaction mixture was shaken with aqueous NH₄Cl and extracted with EtOAc (×3). After the usual workup, the crude material was partially purified by vacuum distillation in a Kügelrohr apparatus (160° C., 0.03 mm Hg). Further purification was achieved by flash chromatography on silica gel using gradient elution (25, 30 and then 50% EtOAc/hexanes) to afford pure ketone 9 as a yellow solid (1.14 g, 53%).

Mp: 106-107° C.; ¹H NMR (500 MHz, CDCl₃): δ 2.51 (s, 6H), 7.54 (d, J=4.9 Hz, 2H), 8.79 (d, J=4.9 Hz, 2H); ¹³C NMR (75 MHz, CDCl₃): δ 14.2, 114.9, 158.8, 159.2, 173.2, 190.7; IR (KBr disc): 1695 cm⁻¹; HRMS: Calcd for C₁₁H₁₀N₄O³²S₂ (M₊) 278.0296, found 278.0289.

Reference Example 3 Compound 11

4-Methoxy-2-pyridone (10) (0.805 g, 6.43 mmol) and freshly distilled POCl₃ (8 mL) were heated at reflux for 15 h. Excess POCl₃ was removed in vacuo and the resultant viscous oil was cooled in ice and carefully neutralised with saturated NaHCO₃ solution. The mixture was extracted with EtOAc (×3) and the extracts were worked up in the standard manner to give a brown oil. This material was partially purified by vacuum distillation in a Kugelrohr apparatus (100° C., 0.07 mm Hg). The distillate was triturated with petroleum ether and a white precipitate was filtered off. The filtrate was concentrated and final purification by flash chromatography on silica gel using 30% EtOAc/hexanes as the eluant gave 2-chloro-4-methoxypyridine (11) as a colourless oil (0.586 g, 63%). 

1. A compound of formula (I):

wherein: R₁ and R₂ are each independently selected from the group consisting of H, OH, OR′, SH, SR′, SOR′, SO₂R′, NO₂, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂, NHSO₂R′, CN, halogen, C(═O)H, C(═O)R′, CO₂H, CO₂R′, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl and substituted or unsubstituted heteroaromatic; and R₃ is selected from the group consisting of H, OH and OMe; wherein the or each group R′ is independently selected from the group consisting of OH, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl, substituted or unsubstituted arylalkenyl and substituted or unsubstituted heteroaromatic, and wherein the group R₁, R₂ or R₃ is a group of formula N(R′)₂ or N(COR′)₂, each of the R′ groups may be the same or different, or the two R′ groups, together with the nitrogen atom to which they are attached, may form a 5-14 membered heterocyclic ring; the aryl group and the aryl moiety of the aralkyl and arylalkenyl group is a carbocyclic aryl group having from 6 to 14 carbon atoms in a carbocyclic ring or two or more fused rings; the aralkyl group is a C₁-C₆ alkyl group which is substituted by an aryl group as defined above; the arylalkenyl group is a C₂-C₆ alkenyl group which is substituted by an aryl group as defined above; the heteroaromatic group is a heterocyclic aromatic group having from 5 to 14 ring atoms in one ring or two or more fused rings of which at least one ring atom is selected from the group consisting of nitrogen, oxygen and sulphur, and such a heterocyclic aromatic group fused with an aryl group as defined above; the substituents on the aryl and heteroaromatic groups and the aryl moiety of the aralkyl and arylalkenyl groups are selected from the group consisting of C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ alkylthio, NH₂, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄ alkanoylamino, di(C₁-C₄ alkanoyl)amino, NO₂, CN and halogen; and derivatives thereof where the nitrogen atom is quaternised, and salts and esters thereof, with the exception of the compounds wherein: R₁ is amino, thiomethyl, methylsulfinyl or methylsulfonyl, R₂ is amino and R₃ is hydrogen; or R₁ and R₂ are amino and R₃ is hydroxy.
 2. A compound according to claim 1, wherein R₁ is selected from the group consisting of OH, OR′, SH, SR′, SOR′, SO₂R′, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂, NHSO₂R′, C(═O)R′, CO₂H, CO₂R′, C₁-C₁₂ alkyl and C₁-C₁₂ haloalkyl, the or each group R′ being independently selected from the group consisting of OH, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, aryl (which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆ alkylamino, di(C₁-C₆ alkyl)amino, NO₂, CN and halogen), aralkyl or arylalkenyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆ alkylamino, di(C₁-C₆ alkyl)amino, NO₂, CN and halogen), and wherein the group R₁ is a group of formula N(R′)₂ or N(COR′)₂, each of the R′ groups may be the same or different, or the two R′ groups, together with the nitrogen atom to which they are attached, form a 5-12 membered heterocyclic ring.
 3. A compound according to claim 1, wherein R₁ is selected from the group consisting of OR′, SR′, SOR′, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂ and NHSO₂R′, the or each group R′ being independently selected from the group consisting of C₁-C₆ alkyl, C₁-C₆ haloalkyl, aryl (which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkenyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), and wherein the group R₁ is a group of formula N(R₁₂ or N(COR′)₂, the two R′ groups, together with the nitrogen atom to which they are attached, may form a 5-10 membered heterocyclic ring.
 4. A compound according to claim 1, wherein R₁ is selected from the group consisting of C₁-C₄ alkoxy, C₁-C₄ alkylthio, C₁-C₄ alkylsulfinyl, amino, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄ alkanoylamino, di(C₁-C₄ alkanoyl)amino, C₁-C₄ haloalkanoylamino, arylamino (wherein the aryl moiety may optionally be substituted with a C₁-C₄ alkoxy group), benzylamino (wherein the phenyl part of the benzyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), cinnamoylamino or dicinnamoylamino (wherein the phenyl part of the or each cinammoyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), or a 5- to 7-membered nitrogen-containing heterocyclic ring attached to the remainder of the molecule via its nitrogen atom.
 5. A compound according to claim 1, wherein R₁ is selected from methoxy, thiomethyl, methylsulfinyl, amino, methylamino, ethylamino, benzylamino, acetylamino, trifluoroacetylamino, diacetylamino, cinnamoylamino, dicinnamoylamino, p-methoxybenzylamino and piperidino.
 6. A compound according to claim 1, wherein R₁ is selected from amino, benzylamino, acetylamino, trifluoroacetylamino, diacetylamino, cinnamoylamino, dicinnamoylamino and p-methoxybenzylamino.
 7. A compound according to claim 1, wherein R₂ is selected from the group consisting of OH, OR′, SH, SR′, SOR′, SO₂R′, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂, NHSO₂R′, C(═O)R′, CO₂H, CO₂R′, C₁-C₁₂ alkyl and C₁-C₁₂ haloalkyl, the or each group R′ being independently selected from the group consisting of OH, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, aryl (which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆ alkylamino, di(C₁-C₆ alkyl)amino, NO₂, CN and halogen), aralkyl or arylalkenyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, NH₂, C₁-C₆ alkylamino, di(C₁-C₆ alkyl)amino, NO₂, CN and halogen), and wherein the group R₂ is a group of formula N(R′)₂ or N(COR′)₂, each of the R′ groups may be the same or different, or the two R′ groups, together with the nitrogen atom to which they are attached, form a 5-12 membered heterocyclic ring.
 8. A compound according to claim 1, wherein R₂ is selected from the group consisting of OR′, SR′, SOR′, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂ and NHSO₂R′, the or each group R′ being independently selected from the group consisting of C₁-C₆ alkyl, C₁-C₆ haloalkyl, aryl (which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), aralkenyl (the aryl moiety of which may optionally be substituted with a group selected from C₁-C₆ alkyl, C₁-C₆ alkoxy and halogen), and wherein the group R₂ is a group of formula N(R′)₂ or N(COR′)₂, the two R′ groups, together with the nitrogen atom to which they are attached, may form a 5-10 membered heterocyclic ring.
 9. A compound according to claim 1, wherein R₂ is selected from the group consisting of C₁-C₄ alkoxy, C₁-C₄ alkylthio, C₁-C₄ alkylsulfinyl, amino, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄ alkanoylamino, di(C₁-C₄ alkanoyl)amino, C₁-C₄ haloalkanoylamino, arylamino (wherein the aryl moiety may optionally be substituted with a C₁-C₄ alkoxy group), benzylamino (wherein the phenyl part of the benzyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), cinnamoylamino or dicinnamoylamino (wherein the phenyl part of the or each cinammoyl moiety may optionally be substituted with a C₁-C₄ alkoxy group), or a 5- to 7-membered nitrogen-containing heterocyclic ring attached to the remainder of the molecule via its nitrogen atom.
 10. A compound according to claim 1, wherein R₂ is selected from thiomethyl, methylsulfinyl, amino, methylamino, ethylamino, acetylamino, diacetylamino, cinnamoylamino, and p-methoxybenzylamino.
 11. A compound according to claim 1, wherein R₂ is selected from amino, acetylamino, diacetylamino and p-methoxybenzylamino.
 12. A compound according to claim 1, wherein R₃ is H.
 13. The following compounds according to claim 1: N′-bisacetyldeoxyvariolin; N′-bisacetyl-N-acetyldeoxyvariolin; N′-bisacetyl-N-bisacetyldeoxyvariolin, N′-acetyldeoxyvariolin; N′-acetyl-N-acetyldeoxyvariolin; N′-biscinnamoyldeoxyvariolin; N′-biscinnamoyl-N-cinnamoyldeoxyvariolin; N′-methanesulfonyldeoxyvariolin; N′-trifluoroacetyldeoxyvariolin; 2′-methoxydeoxyvariolin; 2′-piperidinyldeoxyvariolin; N′-ethyldeoxyvariolin; N′-butyl-N′-methyldeoxyvariolin; and N′-benzyldeoxyvariolin.
 14. A process for producing a compound of formula (I):

wherein: R₁ and R₂ are each independently selected from the group consisting of H, OH, OR′, SH, SR′, SOR′, SO₂R′, NO₂, NH₂, NHR′, N(R′)₂, NHCOR′, N(COR′)₂, NHSO₂R′, CN, halogen, C(═O)H, C(═O)R′, CO₂H, CO₂R′, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl and substituted or unsubstituted heteroaromatic; and R₃ is selected from the group consisting of H, OH and OMe; wherein the or each group R′ is independently selected from the group consisting of OH, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl, substituted or unsubstituted arylalkenyl and substituted or unsubstituted heteroaromatic, and wherein the group R₁, R₂ or R₃ is a group of formula N(R′)₂ or N(COR′)₂, each of the R′ groups may be the same or different, or the two R′ groups, together with the nitrogen atom to which they are attached, may form a 5-14 membered heterocyclic ring; the aryl group and the aryl moiety of the aralkyl and arylalkenyl group is a carbocyclic aryl group having from 6 to 14 carbon atoms in a carbocyclic ring or two or more fused rings; the aralkyl group is a C₁-C₆ alkyl group which is substituted by an aryl group as defined above; the arylalkenyl group is a C₂-C₆ alkenyl group which is substituted by an aryl group as defined above; the heteroaromatic group is a heterocyclic aromatic group having from 5 to 14 ring atoms in one ring or two or more fused rings of which at least one ring atom is selected from the group consisting of nitrogen, oxygen and sulphur, and such a heterocyclic aromatic group fused with an aryl group as defined above; the substituents on the aryl and heteroaromatic groups and the aryl moiety of the aralkyl and arylalkenyl groups are selected from the group consisting of C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ alkylthio, NH₂, C₁-C₄ alkylamino, di(C₁-C₄ alkyl)amino, C₁-C₄ alkanoylamino, di(C₁-C₄ alkanoyl)amino, NO₂, CN and halogen; and derivatives thereof where the nitrogen atom is quaternised, and salts and esters thereof, the process including the production of an intermediate of formula (II)

wherein: R_(1a), R_(2a) and R_(3a) represent any of the groups represented by R₁, R₂ and R₃ respectively, and all such groups where reactive functional groups are protected; and Y₁ and Y₂ are groups capable of being eliminated to produce a fused tricyclic pyridopyrrolopyrimidine ring structure.
 15. A process according to claim 14, wherein Y, is a hydroxy group.
 16. A process according to claim 14 or claim 15, wherein Y₂ is a chlorine atom.
 17. A process according to any one of claims 14 to 16, wherein R_(1a)=R_(2a).
 18. A process according to claim 17, wherein R_(1a) and R_(2a) are methylthio groups.
 19. A process according to any one of claims 14 to 18, further comprising the cyclisation of the intermediate of formula (II) to form an intermediate of formula (III):

wherein R_(1a), R_(2a) and R_(3a) are as defined in claim
 14. 20. A process according to claim 19, the process being acid-catalysed.
 21. A process according to claim 19 or claim 20, when dependent on claim 15, the process comprising reaction of the intermediate of formula (II) with a trialkylsilane of formula R_(a)R_(b)R_(c)SiH wherein R_(a), R_(b) and R_(c) may be the same or different and each represents a C₁-C₁₂ alkyl group or an aryl group as defined in claim
 1. 22. A process according to any one of claims 15 to 18, wherein the intermediate of formula (II) is produced by reacting an intermediate compound of formula (IV):

wherein R_(3a) and Y₂ are as defined in claim 21 and M is a metal, with a compound of formula (V):

wherein R_(1a) and R_(2a) are as defined in claim
 21. 23. A process according to claim 17, when dependent on claim 15, wherein the intermediate of formula (II) is produced by reacting an intermediate compound of formula (VI):

wherein R_(1a) is as defined in claim 14 and M is a metal, with an intermediate compound of formula (VI)

wherein R_(3a) and Y₂ are as defined in claim 14, and Z is a leaving group.
 24. A process according to claim 14, comprising the following steps: a) conversion of a compound of formula (VII):

 where R_(1a) is as defined above and X is a halogen atom, to a compound of formula (VI) as defined in claim 23; b) reaction of a compound of formula (VI) with a compound of formula L₁-CO-L₂, where L₁ and L₂ are the same or different and each represents a leaving group, to give a compound of formula (V) as defined in claim 22; c) reacting the compound of formula (V) with a compound of formula (IV) to form a compound of formula (II) as defined in claim 14; d) cyclization of the compound of formula (II) to form a compound of formula (III) as defined in claim 19; e) if necessary, converting any of the groups represented by R_(1a), R_(2a), and R_(3a) to any of the groups represented by R₁, R₂ and R₃ respectively.
 25. A process according to claim 14, comprising the following steps: a) converting a compound of formula (VIII) as defined in claim 24 to a compound of formula (VI) as defined in claim 23; b) reacting the compound of formula (VI) with a compound of formula (VII) to produce a compound of formula (II) as defined in claim 14; c) cyclization of the compound of formula (II) to form a compound of formula (III) as defined in claim 19; d) if necessary, converting any of the groups represented by R_(1a), R_(2a) and R_(3a) to any of the groups represented by R₁, R₂ and R₃ respectively.
 26. A process for producing a compound of formula (I) wherein R₁ and R₂ are amino groups and R₃ is as defined in claim 1, said process comprising: a) treating a compound of formula (III), wherein R_(1a) and R_(2a) are methylsulfinyl and R_(3a) is as defined in claim 19, with a compound of formula NH₂Prot, where Prot is an amino-protecting group, to give a compound of formula (III), wherein R_(1a) and R₂, are protected amino and R_(3a) is as defined in claim 19, and b) removing the amino-protecting group to give a compound of formula (I) wherein R₁ and R₂ are amino groups and R₃ is as defined in claim
 1. 27. A process for producing a compound of formula (I) wherein R₁ is a methylthio or amino group, R₂ is an amino group and R₃ is as defined in claim 1, from a compound of formula (III), wherein R_(1a) and R_(2a) are methylthio and R_(3a) is as defined in claim 19, said process comprising: a) optionally, oxidising the compound of formula (III) wherein R_(1a) and R_(2a) are methylthio to a compound of formula (III) wherein R_(1a) and R_(2a) are methylsulfinyl; and b) treating the compound of formula (III) wherein R_(1a) and R_(2a) are methylthio or methylsulfinyl with a reagent selected from sodium azide and ammonia.
 28. A pharmaceutical composition comprising an effective amount of a pharmacologically active compound together with a carrier or diluent therefor, wherein said pharmacologically active compound is a compound according to any one of claims 1 to
 13. 29. A compound according to any one of claims 1 to 13 for use as a medicament.
 30. A compound according to any one of claims 1 to 13 for use in the treatment or prophylaxis of cancer.
 31. The use of a compound according to any one of claims 1 to 13 in the manufacture of a medicament for the treatment or prophylaxis of cancer.
 32. A method for the treatment or prophylaxis of cancer in a mammal, which comprises administering to a mammal in need of such treatment an effective amount of a compound according to any one of claims 1 to
 13. 33. A compound of formula (I), as defined in claim 14, for use in the treatment or prophylaxis of cancers selected from ovarian cancer, kidney cancer, prostate cancer, breast cancer and melanoma.
 34. The use of a compound of formula (I), as defined in claim 14, in the manufacture of a medicament for the treatment or prophylaxis of cancers selected from ovarian cancer, kidney cancer, prostate cancer, breast cancer and melanoma.
 35. A method for the treatment or prophylaxis of cancers selected from ovarian cancer, kidney cancer, prostate cancer, breast cancer and melanoma cancer in a mammal, which comprises administering to a mammal in need of such treatment an effective amount of a compound of formula (I), as defined in claim
 14. 36. A compound of formula (II):

wherein R_(1a), R_(a), R_(3a), Y₁ and Y₂ are as defined in claim
 14. 37. A compound according to claim 36, wherein Y, is a hydroxy group.
 38. A compound according to claim 36 or claim 37, wherein Y₂ is a chlorine atom.
 39. A compound according to any one of claims 36 to 38, wherein R_(1a)=R_(2a).
 40. A compound according to claim 39, wherein R_(1a) and R_(2a) are methylthio groups. 